This invention relates to a tag device used mainly to prevent the theft of an article.
As is well-known in the art, these type of tags are attached to articles for sale to prevent them from being taken out of a shop bypassing the cashier. For this purpose, such a tag is provided with an alarm which is adapted to go off if it passes into a detection area installed at the exit of a store. The alarm will also sound if the tag is removed from the article by an unauthorized person.
The alarm function has to be neutralized when necessary, e.g. when changing tags or removing tags to pack the articles. Thus, such tags are provided with an alarm neutralizing mechanism.
A conventional alarm neutralizing mechanism has an extremely simple structure. Namely, merely by inserting a rod-shaped key into a slot formed in the tag, the alarm function is neutralized. Such a key is extremely simple in shape and can be copied easily. Also, a single key is used for many tags. Thus, if such a key should be copied by an unauthorized person, he or she can easily steal goods by using the copied key.
Possible solutions to this problem would be to prepare keys having more complicated shapes or to increase the kinds of keys used. But these solutions would make the handling of the article more difficult because the alarm function cannot be readily neutralized when necessary.
Another problem with a conventional tag is that the corresponding key has to be inserted in the hole in the tag not only to neutralize the alarm function e.g. when removing it from an article for packing, but also to activate it again after attaching the tag to article. Thus, the handling of tags is even more troublesome.
On the other hand, in the detection area at the exit of the store, such a tag is detected making use of electromagnetic waves. Thus, one can easily smuggle merchandise out of the store by covering the tag with a magnetic material.
Also, this detection system often malfunctions and gives off false alarms by reacting to customers' personal belongings instead of tags. Thus, many store owners are reluctant to use such tag detection system, for fear of possible trouble with customers.
An object of this invention is to provide a tag device which can securely detect the theft of an article while overcoming the drawbacks of conventional techniques.